Correct compilation issue

Add includes.
diff --git a/st21nfc/nfc_nci_st21nfc.c b/st21nfc/nfc_nci_st21nfc.c
index 7e14b92..1d69df1 100644
--- a/st21nfc/nfc_nci_st21nfc.c
+++ b/st21nfc/nfc_nci_st21nfc.c
@@ -24,6 +24,7 @@
 #include <errno.h>
 #include <hardware/nfc.h>
 #include <string.h>
+#include <pthread.h>
 
 #include "android_logmsg.h"
 #include "halcore.h"